When I looked at the back wheel with a view to tightening the spokes, I found there were four broken spokes. One, I could live with, but four? So I took off the tire and inner tube, and replaced the four spokes - fortunately, I still have a few left over from last time I bought then from "The Spokesman", because he's no longer in business.
Before I put the tire back on (well, actually, after I put it back on I had second thoughts and took it off again) I put in a gel insert; that adds to the puncture resistance of the tire. With the new spokes, the wheel is pretty solid now. Since most of the biking I do is off-road, on bridleways and suchlike, puncture-resistance is very important to me.
And I added a torque arm to the back wheel. That's because the bike motor tends to twist the hub in it's seating, and if it twists it out, that's a catastrophic prang, because suddenly it's a one-wheeled bike. And the forks are aluminium, which fails suddenly, unlike steel which at least give you a bit of warning because it deforms before it breaks - aluminium just cracks. The torque arm transmits the motor torque to the bike fram, using a thick steel arm.
I also tidied up the wiring, using a curly-wurly cable tidy to make it all look neat. I installed a bike speedometer, and today I took it out for a run. It runs very nicely. It has good acceleration from a standstill (which is important when caching because I do a lot of stopping and starting). The acceleration is so good, that when I started off at the bottom of the hill I live on, the front wheel tried to come up off the ground! And the three-speed switch lets me run in granny mode, 3/4 speed or full-on. Ganny mode is, of course the most economical, but when I'm on the way back to the car and I know I have a lot of battery left, and when I'm feeling tired from the day out, I can switch over to full-on and take it easy.
The weight of bike.4 is good at 46.8 pounds, including back rack, controller and wiring, but not including batteries. The bike I'm mostly using now, bike.1 is 57.8 pounds, 11 pounds more.
I also tried reprogramming the controller to allow more amps through the motor, but it didn't seem to make any difference; I guess the motor is already taking as many amps as it can handle (and when I felt it, it wasn't even warm, which is good). And I'm happy with the power of the bike, so no need to tinker.
One thing I did do - I ran a huge pair of cables (4 sq mm) from the battery up to the handlebars, where I put an ammeter, and another huge pair of cables back to the controller. That means I can watch the current consumption as I trundle along. It's ugly and horrible. I won't be leaving that in place permanently, but it's good for the testing phase that I'm now in.
On Ebay again, I treated myself to a new set of engineer's metal files, the ones I have, inherited from my father, are very worn. And I bought some more spokes. And some connectors, for joining wires up in a way that lets you easily separate them when needed.
Tomorrow the weather forecast is good all day, so I'm planning to go to Cambridge to make a start on the Cambs Cachathon.